In order to solve the problem that the traditional loss reduction measures are difficult to meet the line loss rate requirements under the condition of high energy consumption and low power factor, and realize the network-based line loss management method, this paper proposes an optimal combination model of distribution network lines. Firstly, the application scenarios and problems in the online loss management of the line loss electric quantity optimization distribution method are expounded, and the optimal combination model of the line is constructed according to the scene and application requirements. Then, the line combination optimization algorithm is proposed, aiming at maximizing the number of lines with the line loss rate meeting the assessment requirements, taking the line loss rate evaluation standard as the constraint condition and using GAMS to solve the problem. The results of the example show that the model can effectively determine the transfer direction of the high-loss load of the distribution network, and provide a reliable basis for subsequent network reconstruction and network planning.